Two-Speed Transmission For Electric Vehicle

ABSTRACT

A two-speed transmission for a vehicle is provided including a planetary gear set selectively coupling an input shaft and an output shaft. The planetary gear set is configured to provide two forward gear ratios and neutral. The planetary gear set includes at least one sun gear, at least one pinion in meshing engagement with the sun gear, at least one ring gear meshingly engaged with the pinion, and a carrier. The carrier supports the pinion and is connected to the output shaft such that rotation of the carrier drives the output shaft. The two-speed transmission also includes one or more elements that rotatably couple different combinations of the sun gear, the pinion, the ring gear, the input shaft, and the carrier with one another or a ground. Such elements may include combinations of clutches, brakes, and dog clutches.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/560,697 filed on Dec. 4, 2014 and claims the benefit of U.S.Provisional Application No. 61/912,163, filed on Dec. 5, 2013. Theentire disclosure of each of the above applications is incorporatedherein by reference.

FIELD

The present disclosure relates to a two-speed transmission for avehicle, and more particularly, to a two-speed transmission for anelectric vehicle.

BACKGROUND

Electric vehicles are typically driven by electric motors that rely onbatteries for electrical power. Electricity may be supplied to thebatteries for storage from a variety of different sources. For example,electricity may be supplied to the batteries of an electric vehicle by acharger that is plugged into an electrical transmission network (i.e. anelectrical power grid), by electricity generated by an internalcombustion engine, by electricity produced by regenerative vehiclebraking, and/or by solar panels mounted on the electric vehicle.

Existing electric vehicles typically utilize a fixed ratio, single-speedtransmission that provides one forward gear. Such electric vehicles arefitted with relatively large electric motors such that there issufficient torque to launch the vehicle from a standing stop and enoughpower to drive the vehicle to highway speeds. These large electricmotors require a large amount of electricity to properly operate.Accordingly, large arrays of batteries are generally required forextended operation of a conventional electric vehicle. The foremostlimitation of electric vehicles is the cost and size of the batteries.Batteries are both heavy and expensive, thereby setting practical limitsto the range of electrical vehicles. What is needed is a way to makeelectric vehicles more efficient such that the range can be increasedwithout the need for additional batteries and their associated weightand cost trade-offs.

SUMMARY

The subject disclosure provides a two-speed transmission for a vehicleand more particularly, a two-speed transmission for an electric vehicle.Generally, the two-speed transmission includes an input shaft having afirst end for connection with an electric motor for powering the vehicleand a second end opposite the first end. An output shaft is alsoprovided for connection with a final drive unit of the vehicle. Aplanetary gear set selectively couples the input shaft and the outputshaft. The planetary gear set provides two forward gear ratios andneutral. The planetary gear set includes at least one sun gear connectedto the input shaft between the first end of the input shaft and thesecond end of the input shaft. At least one pinion is disposed radiallyoutwardly of the at least one sun gear such that the at least one pinionis in meshing engagement with the at least one sun gear. The planetarygear set also includes at least one ring gear meshingly engaged with theat least one pinion. The at least one ring gear circumscribes at least aportion of the at least one pinion. The planetary gear set furtherincludes a carrier connected to the output shaft such that rotation ofthe carrier drives the output shaft. The carrier also supports the atleast one pinion radially about the at least one sun gear.

The two-speed transmission also includes one or more elements thatrotatably couple different combinations of the at least one sun gear,the at least one pinion, the at least one ring gear, the input shaft,and the carrier with one another or to a ground such as a transmissionhousing. These elements may include various combinations of clutches,multi-plate wet clutch assemblies, brakes, and dog clutches. The variousconfigurations of these elements are described more fully below andresults in unique power flows through the two-speed transmission.

Advantageously, the two-speed transmission, in all of the configurationsdescribed below, provides extended range for electric vehicles whencompared with single gear ratio transmissions for any given batterysize. The two-speed transmission disclosed allows for a smaller electricmotor to be fitted in the electric vehicle because the first gear ratiocan provide sufficient torque to launch the electric vehicle with thesmaller electric motor and the second gear ratio provides sufficientpower to drive the vehicle to highway speeds. The disclosed power flowsreduce the number of mechanical components and control components andprovide a two-speed transmission with minimal energy losses.Accordingly, battery size and cost can be further reduced with the useof smaller electric motors.

DRAWINGS

The features and advantages described above and other features andadvantages of the present disclosure will be readily appreciated, as thesame becomes better understood by reference to the following detaileddescription when considered in connection with the accompanyingdrawings. These drawings are for illustrative purposes of only selectembodiments and not all possible implementations and are not intended tolimit the scope of the present disclosure, wherein:

FIG. 1 is a transmission power flow diagram illustrating an exemplarytwo-speed transmission constructed in accordance with the subjectdisclosure;

FIG. 2 is a transmission power flow diagram illustrating anotherexemplary two-speed transmission constructed in accordance with thesubject disclosure;

FIG. 3 is a transmission power flow diagram illustrating anotherexemplary two-speed transmission constructed in accordance with thesubject disclosure;

FIG. 4 is a transmission power flow diagram illustrating anotherexemplary two-speed transmission constructed in accordance with thesubject disclosure;

FIG. 5 is a transmission power flow diagram illustrating anotherexemplary two-speed transmission constructed in accordance with thesubject disclosure;

FIG. 6 is a transmission power flow diagram illustrating anotherexemplary two-speed transmission constructed in accordance with thesubject disclosure;

FIG. 7 is a transmission power flow diagram illustrating anotherexemplary two-speed transmission constructed in accordance with thesubject disclosure;

FIG. 8 is a transmission power flow diagram illustrating anotherexemplary two-speed transmission constructed in accordance with thesubject disclosure; and

FIG. 9 is a transmission power flow diagram illustrating anotherexemplary two-speed transmission constructed in accordance with thesubject disclosure.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings. Example embodiments are provided so that thisdisclosure will be thorough, and will fully convey the scope to thosewho are skilled in the art. Numerous specific details are set forth suchas examples of specific components, devices, and methods, to provide athorough understanding of embodiments of the present disclosure. It willbe apparent to those skilled in the art that specific details need notbe employed, that example embodiments may be embodied in many differentforms and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

When an element or layer is referred to as being “on,” “engaged to,”“connected to,” or “coupled to” another element or layer, it may bedirectly on, engaged, connected or coupled to the other element orlayer, or intervening elements or layers may be present. In contrast,when an element is referred to as being “directly on,” “directly engagedto,” “directly connected to,” or “directly coupled to” another elementor layer, there may be no intervening elements or layers present. Otherwords used to describe the relationship between elements should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” etc.). As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items.

Although the terms first, second, third, etc. may be used herein todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections should notbe limited by these terms. These terms may be only used to distinguishone element, component, region, layer or section from another region,layer or section. Terms such as “first,” “second,” and other numericalterms when used herein do not imply a sequence or order unless clearlyindicated by the context. Thus, a first element, component, region,layer or section discussed below could be termed a second element,component, region, layer or section without departing from the teachingsof the example embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,”“lower,” “above,” “upper,” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. Spatiallyrelative terms may be intended to encompass different orientations ofthe device in use or operation in addition to the orientation depictedin the figures. For example, if the device in the figures is turnedover, elements described as “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the example term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

Referring to the figures generally, several configurations and powerflows for a two-speed transmission 20 are presented. Such transmissions20 may find utility when coupled with an electric motor powering avehicle by improving the efficiency of the vehicle while concurrentlyreducing cost. These new results are achieved because the disclosedpower flows enable vehicle launch and high-speed driving using a smallerelectric motor. Two forward gear ratios are provided to supplysufficient torque to launch the vehicle in a lower gear ratio and tosupply sufficient rotational speed for highway driving in a higher gearratio. Accordingly, a smaller electric motor can be fitted in thevehicle, which has reduced energy consumption over large electricmotors. Thus, the range of the electric vehicle can be increased for agiven battery size. Alternatively, smaller batteries can be fitted tothe vehicle without decreasing range, which reduces the overall weightand cost of the vehicle. The weight reduction advantages and the reducedenergy consumption of smaller electric motors yield increases inefficiency.

Referring to FIG. 1, the two-speed transmission 20 illustrated iscoupled to a final drive unit 22 such as a differential. The final driveunit 22 operates to direct power from the two-speed transmission 20 toone or more wheels of the vehicle. The two-speed transmission 20includes an input shaft 24 and an output shaft 26. The input shaft 24has a first end 28 and a second end 30. The first end 28 of the inputshaft 24 is provided to couple with the electric motor of the vehicle.The second end 30 of the input shaft 24 is axially spaced from the firstend 28 of the input shaft 24. The output shaft 26 is provided to couplewith the final drive unit 22 of the vehicle. An output gear set 32 isdisposed between the output shaft 26 and the final drive unit 22.Rotation of the output shaft 26 drives rotation of the output gear set32 and, thus, the final drive unit 22.

The two-speed transmission 20 includes a planetary gear set 34selectively coupling the input shaft 24 and the output shaft 26. Theplanetary gear set 34 includes a sun gear 36, at least one double steppinion 38, a ring gear 40, and a carrier 42. The sun gear 36 isconnected to the input shaft 24 proximate to the second end 30 of theinput shaft 24. It should be appreciated that the sun gear 36 need notbe disposed at the second end 30 of the input shaft 24. Instead, theinput shaft 24 may extend beyond the sun gear 36 in a direction towardthe output shaft 26.

The at least one double step pinion 38 has a first gear 44 and a secondgear 46. The second gear 46 of the at least one double step pinion 38 isrotatably fixed with the first gear 44 of the at least one double steppinion 38 where rotation of the first gear 44 produces like rotation ofthe second gear 46. The first gear 44 of the at least one double steppinion 38 has a first outer diameter and the second gear 46 of the atleast one double step pinion 38 has a second outer diameter. The secondouter diameter of the second gear 46 is less than the first outerdiameter of the first gear 44. In other words, the first gear 44 of theat least one double step pinion 38 has a larger circumference than thesecond gear 46 of the at least one double step pinion 38.

The first gear 44 of the at least one double step pinion 38 is meshinglyengaged with the sun gear 36 and is disposed radially outwardly of thesun gear 36. The second gear 46 of the at least one double step pinion38 is meshingly engaged with the ring gear 40. As such, the ring gear 40generally circumscribes the second gear 46 of the at least one doublestep pinion 38. The carrier 42 of the planetary gear set 34 supports theat least one double step pinion 38 and is connected to the output shaft26. Accordingly, the second gear 46 of the at least one double steppinion 38 can run along the ring gear 40 such that the second gear 46 ofthe at least one double step pinion 38 orbits within the ring gear 40along with the carrier 42. However, it should be appreciated that the atleast one double step pinion 38 is free to rotate with respect to thecarrier 42.

The two-speed transmission 20 in FIG. 1 includes a dog clutch 48disposed adjacent the ring gear 40 of the planetary gear set 34. The dogclutch 48 presents a plurality of teeth (not shown) that interlockinglyengage with the ring gear 40 when the dog clutch 48 is actuated.Accordingly, when the dog clutch 48 is engaged, the dog clutch 48 doesnot permit slip of the ring gear 40. It should further be appreciatedthat the teeth of the dog clutch 48 may directly engage the ring gear 40or alternatively may engage another component that is rotatably fixedwith the ring gear 40.

The two-speed transmission 20 also includes a multi-plate wet clutchassembly 50 including a brake 52 and a clutch 54. The brake 52 is fixedto a ground 56 such as a housing (not shown) of the two-speedtransmission 20. The brake 52 includes a brake friction plate 58connected to the dog clutch 48. The brake 52 provides a first gear ratioof the two-speed transmission 20 by selectively engaging the brakefriction plate 58. When the brake 52 selectively engages the brakefriction plate 58, the brake 52 resists rotation of the brake frictionplate 58 with respect to the ground 56. This correspondingly restrictsrotation of the ring gear 40 with respect to the ground 56 when the dogclutch 48 is engaged with the ring gear 40. More particularly, the brake52 may include a brake caliper 60 that selectively engages the brakefriction plate 58. The brake caliper 60 may be fixed to the ground 56such as the housing of the two-speed transmission 20.

The clutch 54 includes a clutch friction plate 62 connected to the inputshaft 24 between the first end 28 of the input shaft 24 and the sun gear36 of the planetary gear set 34. The clutch 54 is connected to thecarrier 42 of the planetary gear set 34. Accordingly, the clutch 54provides a second gear ratio of the two-speed transmission 20 byselectively engaging the clutch friction plate 62 to rotatably couplethe input shaft 24 and the sun gear 36 with the carrier 42. Moreparticularly, the clutch 54 may include a clutch caliper 64 thatselectively engages the clutch friction plate 62. The clutch caliper 64may be connected to the carrier 42 of the planetary gear set 34. Itshould be appreciated that unlike the dog clutch 48, the brake 52 andthe clutch 54 may allow some slip if desired. It should also beappreciated that the dog clutch 48 can advantageously disconnect thebrake 52 from the ring gear 40 such that friction and inertia lossesassociated with rotating the brake friction plate 58 can be eliminatedwhen the dog clutch 48 is not selectively engaged.

The multi-plate wet clutch assembly 50 of the two-speed transmission 20provides a neutral state in response to the clutch 54 permitting freerotation of the clutch friction plate 62 and the brake 52 permittingfree rotation of the brake friction plate 58 when the dog clutch 48 isnot engaged. In the neutral state, input shaft 24 and the sun gear 36rotate and drive rotation of the first gear 44 of the at least onedouble step pinion 38. Rotation of the at least one double step pinion38 and thus the second gear 46 drives rotation of the ring gear 40. Thering gear 40 rotates freely in the neutral state because the dog clutch48 and the brake 52 are not engaged. Thus, all of the torque supplied tothe input shaft 24 goes to rotating the ring gear 40 so the carrier 42is not rotationally driven. The carrier 42 is connected to the outputshaft 26 so the output shaft 26 is not rotationally driven in theneutral state.

The first gear ratio is provided in response to the clutch 54 permittingfree rotation of the clutch friction plate 62 and the brake 52selectively engaging the brake friction plate 58 when the dog clutch 48is engaged. The brake 52 and the dog clutch 48 lock the ring gear 40 inplace so that the ring gear 40 remains stationary with respect to theground 56. As the input shaft 24 and the sun gear 36 rotate and drivethe first gear 44 of the at least one double step pinion 38, the atleast one double step pinion 38 orbits within the ring gear 40,traveling in a circular arc, as the second gear 46 of the at least onedouble step pinion 38 runs along the ring gear 40. This orbital movementof the at least one double step pinion 38 with respect to the ring gear40 drives rotation of the carrier 42 and thus the output shaft 26 at arotational speed that is different than a rotational speed of the inputshaft 24.

The second gear ratio is provided in response to the clutch 54selectively engaging the clutch friction plate 62 and the brake 52permitting free rotation of the brake friction plate 58 when the dogclutch 48 is not engaged. The clutch 54 locks rotation of the carrier 42with the input shaft 24. Therefore, the carrier 42 and thus the outputshaft 26 rotate at the same rotational speed as the input shaft 24.Accordingly, the second gear ratio may be a 1:1 ratio. It should also benoted that the dog clutch 48 is selectively disengaged from the ringgear 40 either before or during the clutch 54 engagement associated withan up-shift of the two-speed transmission 20 from the first gear ratioto second gear ratio (the 1-2 shift). By contrast, the dog clutch 48 isselectively engaged with the ring gear 40 either after or during theclutch 54 disengagement associated with a down-shift of the two-speedtransmission 20 from the second gear ratio to the first gear ratio (the2-1 shift) or from the second gear ratio to neutral (the 2-N shift). Thedifference in rotational speed of the output shaft 26 produced by thesecond gear ratio relative to the first gear ratio may be referred to asa gear ratio spread, which is vehicle and motor specific.

In another form of the configuration shown in FIG. 1, the two-speedtransmission 20 may also include one or more idler gears (not shown).For example, an idler gear may be disposed between the first gear 44 ofthe at least one double step pinion 38 and the sun gear 36. Alternatelyor additionally, an idler gear may be disposed between the second gear46 of the at least one double step pinion 38 and the ring gear 40. Itshould be appreciated that the idler gear(s) may be used to change thegear ratio spread between the first gear ratio and the second gear ratioand/or reverse the direction of rotation. In yet another form of theconfiguration show in FIG. 1, the at least one double step pinion 38 maybe replaced by at least one single pinion gear (not shown) where atwo-speed transmission 20 having a high reduction ratio is notnecessary.

Now referring to FIG. 2, the two-speed transmission 20 illustrated inFIG. 1 can be modified where the dog clutch 48 and brake 52 are replacedby a band brake 66. In the configuration shown in FIG. 2, the band brake66 of the two-speed transmission 20 is fixed to the ground 56 andincludes a brake drum 68 connected to the ring gear 40. The band brake66 provides the first gear ratio by selectively engaging the brake drum68 to resist rotation of the ring gear 40 with respect to the ground 56.The clutch 54 is again connected to the carrier 42 of the planetary gearset 34 and the clutch friction plate 62 is connected to the input shaft24 between the first end 28 of the input shaft 24 and the sun gear 36 ofthe planetary gear set 34. The clutch 54 provides the second gear ratioby selectively engaging the clutch friction plate 62 to rotatably couplethe input shaft 24 and the sun gear 36 with the carrier 42.

The multi-plate wet clutch assembly 50 of the two-speed transmission 20provides neutral in response to the band brake 66 permitting freerotation of the brake drum 68 and the clutch 54 permitting free rotationof the clutch friction plate 62. In the neutral state, input shaft 24and the sun gear 36 rotate and drive rotation of the first gear 44 ofthe at least one double step pinion 38. Rotation of the at least onedouble step pinion 38 and thus the second gear 46 drives rotation of thering gear 40. The ring gear 40 rotates freely in the neutral statebecause the band brake 66 is not engaged. Thus, all of the torquesupplied to the input shaft 24 goes to rotating the ring gear 40 so thecarrier 42 is not rotationally driven. The carrier 42 is connected tothe output shaft 26 so the output shaft 26 is not rotationally driven inthe neutral state.

The first gear ratio is provided in response to the band brake 66selectively engaging the brake drum 68 and the clutch 54 permitting freerotation of the clutch friction plate 62. The band brake 66 locks thering gear 40 in place so that the ring gear 40 remains stationary withrespect to the ground 56. As the input shaft 24 and the sun gear 36rotate and drive the first gear 44 of the at least one double steppinion 38, the at least one double step pinion 38 orbits within the ringgear 40, traveling in a circular arc, as the second gear 46 of the atleast one double step pinion 38 runs along the ring gear 40. Thisorbital movement of the at least one double step pinion 38 with respectto the ring gear 40 drives rotation of the carrier 42 and thus theoutput shaft 26 at a rotational speed that is different than arotational speed of the input shaft 24. The second gear ratio isprovided in response to the band brake 66 permitting free rotation ofthe brake drum 68 and the clutch 54 selectively engaging the clutchfriction plate 62. The clutch 54 locks rotation of the carrier 42 withthe input shaft 24. Therefore, the carrier 42 and thus the output shaft26 rotate at the same rotational speed as the input shaft 24.Accordingly, the second gear ratio may be a 1:1 ratio.

In another form of the configuration shown in FIG. 2, the two-speedtransmission 20 may also include one or more idler gears (not shown).For example, an idler gear may be disposed between the first gear 44 ofthe at least one double step pinion 38 and the sun gear 36.Alternatively or additionally, an idler gear may be disposed between thesecond gear 46 of the at least one double step pinion 38 and the ringgear 40.

Now referring to FIG. 3, the two-speed transmission 20 illustrated inFIG. 2 can be modified where the at least one double step pinion 38 isreplaced by at least one single pinion gear 70. Particularly, such aconfiguration may be used where a two-speed transmission 20 having ahigh reduction ratio is not necessary. In the configuration shown inFIG. 3, the at least one single pinion gear 70 is meshingly engaged withthe sun gear 36 and the ring gear 40. As such, the at least one singlepinion gear 70 is disposed radially outwardly of the sun gear 36 and thering gear 40 circumscribes the at least one single pinion gear 70 andthe sun gear 36. It should be appreciated that multiple single piniongears may be disposed about the sun gear 36 without departing from thesubject disclosure. The carrier 42 of the planetary gear set 34 stillsupports the at least one single pinion gear 70 and is connected to theoutput shaft 26 and the clutch 54.

As with the configuration illustrated in FIG. 2, the band brake 66 ofthe configuration in FIG. 3 provides a first gear ratio by selectivelyengaging the brake drum 68 to resist rotation of the ring gear 40 withrespect to the ground 56. The band brake 66 locks the ring gear 40 inplace so that the ring gear 40 remains stationary with respect to theground 56. As the input shaft 24 and the sun gear 36 rotate and drivethe at least one single pinion gear 70, which orbits within the ringgear 40, traveling in a circular arc, as the at least one single piniongear 70 runs along the ring gear 40. This orbital movement of the atleast one single pinion gear 70 with respect to the ring gear 40 drivesrotation of the carrier 42 and thus the output shaft 26 at a rotationalspeed that is different than a rotational speed of the input shaft 24.

The clutch 54 provides a second gear ratio by selectively engaging theclutch friction plate 62 to rotatably couple the input shaft 24 and thesun gear 36 with the carrier 42. The clutch 54 locks rotation of thecarrier 42 with the input shaft 24. Therefore, the carrier 42 and thusthe output shaft 26 rotate at the same rotational speed as the inputshaft 24. Accordingly, the second gear ratio may be a 1:1 ratio. Theband brake 66 and the clutch 54 provides neutral in response to the bandbrake 66 permitting free rotation of the brake drum 68 and the clutch 54permitting free rotation of the clutch friction plate 62. In the neutralstate, input shaft 24 and the sun gear 36 rotate and drive rotation ofthe at least one single pinion gear 70. Rotation of the at least onesingle pinion gear 70 drives rotation of the ring gear 40. The ring gear40 rotates freely in the neutral state because the band brake 66 is notengaged. Thus, all of the torque supplied to the input shaft 24 goes torotating the ring gear 40 so the carrier 42 is not rotationally driven.The carrier 42 is connected to the output shaft 26 so the output shaft26 is not rotationally driven in the neutral state.

In another form of the configuration shown in FIG. 3, the two-speedtransmission 20 may also include one or more idler gears. For example,an idler gear (not shown) may be disposed between the at least onesingle pinion gear 70 and the sun gear 36. Alternatively oradditionally, an idler gear (not shown) may be disposed between the atleast one single pinion gear 70 and the ring gear 40.

Now referring to FIG. 4, the two-speed transmission 20 illustrated inFIG. 1 can be modified where the dog clutch 48 is replaced by amechanical diode 72. It should be appreciated that the mechanical diode72 functions as a one way clutch. Although the structure of themechanical diode 72 may take a variety of different forms, in oneexample, the mechanical diode 72 has five basic components. Thesecomponents include a notch plate, a pocket plate, a plurality of struts,a plurality of springs, and a retaining ring. The notch plate and thepocket plate may generally be cylindrical and are co-axially disposed ina nested relationship. The notch plate has a plurality of notches andthe pocket plate has a plurality of pockets that are arranged oppositethe plurality of notches of the notch plate. The plurality of struts arepivotally connected to the pocket plate and are partially disposed inthe plurality of pockets of the pocket plate. The plurality of springsare disposed in the plurality of pockets of the pocket plate such thatthe plurality of springs extend between the plurality of struts and thepocket plate. The plurality of springs bias the plurality of struts toan extended position where the plurality of struts project outwardlyfrom the plurality of pockets to engage the plurality of notches of thenotch plate. The plurality of struts slide over the plurality of notchesin a first rotational direction, thus allowing clutch slip in the firstrotational direction. However, the plurality of struts engage theplurality of notches in a second rotational direction, thus providingclutch lock-up in the second rotational direction. The retaining ring isdisposed between the notch plate and the pocket plate and holds thenotch plate and the pocket plate in place so that the notch plate cannotmove axially relative to the pocket plate.

In the configuration shown in FIG. 4, the mechanical diode 72 isconnected to the ring gear 40 and provides selective engagement of thering gear 40. The two-speed transmission 20 has a multi-plate wet clutchassembly 50 including a brake 52 fixed to the ground 56 and a clutch 54connected to the carrier 42. The brake 52 includes a brake frictionplate 58 connected to the mechanical diode 72. Thus, the brake 52provides a first gear ratio by selectively engaging the brake frictionplate 58 to resist rotation of the ring gear 40 with respect to theground 56 when the mechanical diode 72 is engaged with the ring gear 40.Again, the clutch 54 provides a second gear ratio by selectivelyengaging the clutch friction plate 62 to rotatably couple the inputshaft 24 and the sun gear 36 with the carrier 42.

The multi-plate wet clutch assembly 50 of the two-speed transmission 20shown in FIG. 4 provides a neutral state in response to the clutch 54permitting free rotation of the clutch friction plate 62 and the brake52 permitting free rotation of the brake friction plate 58 when themechanical diode 72 is not engaged. In the neutral state, input shaft 24and the sun gear 36 rotate and drive rotation of the first gear 44 ofthe at least one double step pinion 38. Rotation of the at least onedouble step pinion 38 and thus the second gear 46 drives rotation of thering gear 40. The ring gear 40 rotates freely in the neutral statebecause the mechanical diode 72 and the brake 52 are not engaged. Thus,all of the torque supplied to the input shaft 24 goes to rotating thering gear 40 so the carrier 42 is not rotationally driven. The carrier42 is connected to the output shaft 26 so the output shaft 26 is notrotationally driven in the neutral state.

The first gear ratio is provided in response to the clutch 54 permittingfree rotation of the clutch friction plate 62 and the brake 52selectively engaging the brake friction plate 58 when the mechanicaldiode 72 is engaged. The brake 52 and the mechanical diode 72 lock thering gear 40 in place so that the ring gear 40 remains stationary withrespect to the ground 56. As the input shaft 24 and the sun gear 36rotate and drive the first gear 44 of the at least one double steppinion 38, the at least one double step pinion 38 orbits within the ringgear 40, traveling in a circular arc, as the second gear 46 of the atleast one double step pinion 38 runs along the ring gear 40. Thisorbital movement of the at least one double step pinion 38 with respectto the ring gear 40 drives rotation of the carrier 42 and thus theoutput shaft 26 at a rotational speed that is different than arotational speed of the input shaft 24. The second gear ratio isprovided in response to the clutch 54 selectively engaging the clutchfriction plate 62 and the brake 52 permitting free rotation of the brakefriction plate 58 when the mechanical diode 72 is not engaged. Theclutch 54 locks rotation of the carrier 42 with the input shaft 24.Therefore, the carrier 42 and thus the output shaft 26 rotate at thesame rotational speed as the input shaft 24. Accordingly, the secondgear ratio may be a 1:1 ratio.

In another form of the configuration shown in FIG. 4, the two-speedtransmission 20 may also include one or more idler gears (not shown).For example, an idler gear may be disposed between the first gear 44 ofthe at least one double step pinion 38 and the sun gear 36.Alternatively or additionally, an idler gear may be disposed between thesecond gear 46 of the at least one double step pinion 38 and the ringgear 40.

Now referring to FIG. 5, another configuration of a two-speedtransmission 20 is illustrated. Again, the two-speed transmission 20includes an input shaft 24 having a first end 28 for connection with theelectric motor and a second end 30 opposite the first end 28. An outputshaft 26 for connection with the final drive unit 22 of the vehicle isalso provided. An output gear set 32 is disposed between the outputshaft 26 and the final drive unit 22. A planetary gear set 34selectively couples the input shaft 24 and the output shaft 26 where theplanetary gear set 34 includes a sun gear 36, at least one double steppinion 38, and a carrier 42. The sun gear 36 is connected to the inputshaft 24 proximate to the second end 30 of the input shaft 24. The atleast one double step pinion 38 has a first gear 44 and a second gear 46rotatably fixed with the first gear 44. The first gear 44 has a firstouter diameter and the second gear 46 has a second outer diameter. Thesecond outer diameter of the second gear 46 is less than the first outerdiameter of the first gear 44. The first gear 44 of the at least onedouble step pinion 38 is meshingly engaged with the sun gear 36 and isdisposed radially outwardly of the sun gear 36.

A first ring gear 74 is meshingly engaged with the first gear 44 of theat least one double step pinion 38. As such, the first ring gear 74circumscribes the first gear 44 of the at least one double step pinion38 and the sun gear 36. A second ring gear 76 is meshingly engaged withthe second gear 46 of the at least one double step pinion 38 andcircumscribes the second gear 46 of the at least one double step pinion38. The planetary gear set 34 includes a carrier 42 supporting the atleast one double step pinion 38. Also, the carrier 42 is connected tothe output shaft 26 and drives the output shaft 26 when rotated.

A first mechanical diode 78 is connected to the first ring gear 74 andprovides selective engagement of the first ring gear 74. A secondmechanical diode 80 is connected to the second ring gear 76 and providesselective engagement of the second ring gear 76. The two-speedtransmission 20 also has a multi-plate wet clutch assembly 50. Themulti-plate wet clutch assembly 50 includes a first brake 82 that isfixed to a ground 56 and a second brake 84 that is also fixed to theground 56. The ground 56 remains stationary with respect to rotation ofthe input shaft 24 and the output shaft 26. Again, the ground 56 may bea housing of the two-speed transmission 20, for example. The first brake82 includes a first brake friction plate 86 connected to the firstmechanical diode 78. The second brake 84 includes a second brakefriction plate 88 connected to the second mechanical diode 80.

The multi-plate wet clutch assembly 50 provides a first gear ratio inresponse to the second brake 84 selectively engaging the second brakefriction plate 88 and the second mechanical diode 80 engaging the secondring gear 76. Thus, in the first gear ratio, the multi-plate wet clutchassembly 50 resists rotation of the second ring gear 76 with respect tothe ground 56. The multi-plate wet clutch assembly 50 provides a secondgear ratio in response to the first brake 82 selectively engaging thefirst brake friction plate 86 and the first mechanical diode 78 engagingthe first ring gear 74. Accordingly, in the second gear ratio, themulti-plate wet clutch assembly 50 resists rotation of the first ringgear 74 with respect to the ground 56.

The multi-plate wet clutch assembly 50 provides a neutral state inresponse to the first brake 82 permitting free rotation of the firstbrake friction plate 86 and the second brake 84 permitting free rotationof the second brake friction plate 88. In the neutral state, input shaft24 and the sun gear 36 rotate and drive rotation of the first gear 44 ofthe at least one double step pinion 38. Rotation of the at least onedouble step pinion 38 drives rotation of the first ring gear 74 and thesecond ring gear 76. The first ring gear 74 and the second ring gear 76rotate freely in the neutral state because the first and secondmechanical diodes 78, 80 and the first and second brakes 82, 84 are notengaged. Thus, all of the torque supplied to the input shaft 24 goes torotating the first and second ring gears 74, 76 so the carrier 42 is notrotationally driven. The carrier 42 is connected to the output shaft 26so the output shaft 26 is not rotationally driven in the neutral state.

The first gear ratio is provided in response to the first brake 82permitting free rotation of the first brake friction plate 86 when thefirst mechanical diode 78 is disengaged and the second brake 84selectively engaging the second brake friction plate 88 when the secondmechanical diode 80 is engaged. The second brake 84 and the secondmechanical diode 80 lock the second ring gear 76 in place so that thesecond ring gear 76 remains stationary with respect to the ground 56. Asthe input shaft 24 and the sun gear 36 rotate and drive the first gear44 of the at least one double step pinion 38, the at least one doublestep pinion 38 orbits within the second ring gear 76, traveling in acircular arc, as the second gear 46 of the at least one double steppinion 38 runs along the second ring gear 76. This orbital movement ofthe at least one double step pinion 38 with respect to the second ringgear 76 drives rotation of the carrier 42 and thus the output shaft 26at a rotational speed that may be different than a rotational speed ofthe input shaft 24. At the same time, the first ring gear 74 is allowedto freely rotate.

The second gear ratio is provided in response to the first brake 82selectively engaging the first brake friction plate 86 when the firstmechanical diode 78 is engaged and the second brake 84 permitting freerotation of the second brake friction plate 88 when the secondmechanical diode 80 is disengaged. The first brake 82 and the firstmechanical diode 78 lock the first ring gear 74 in place so that thefirst ring gear 74 remains stationary with respect to the ground 56. Asthe input shaft 24 and the sun gear 36 rotate and drive the first gear44 of the at least one double step pinion 38, the at least one doublestep pinion 38 orbits within the first ring gear 74, traveling in acircular arc, as the first gear 44 of the at least one double steppinion 38 runs along the first ring gear 74. This orbital movement ofthe at least one double step pinion 38 with respect to the first ringgear 74 drives rotation of the carrier 42 and thus the output shaft 26at a rotational speed that may be different than a rotational speed ofthe input shaft 24. At the same time, the first ring gear 74 is allowedto freely rotate. At the same time, the second ring gear 76 is allowedto freely rotate.

In another form of the configuration shown in FIG. 5, the two-speedtransmission 20 may also include one or more idler gears (not shown).For example, an idler gear may be disposed between the first gear 44 ofthe at least one double step pinion 38 and the sun gear 36.Alternatively or additionally, an idler gear may be disposed between thefirst gear 44 of the at least one double step pinion 38 and the firstring gear 74. Similarly, an idler gear may be disposed between thesecond gear 46 of the at least one double step pinion 38 and the secondring gear 76. It should be appreciated that one or none of the idlergears described above may be included in the two-speed transmission 20.It should also be appreciated that various combinations of the idlergears described above may be employed where all such combinations areconsidered to be within the scope of the subject disclosure.

Now referring to FIG. 6, another configuration of a two-speedtransmission 20 is illustrated. Again, the two-speed transmission 20includes an input shaft 24 having a first end 28 for connection with theelectric motor powering the vehicle and a second end 30 opposite thefirst end 28. An output shaft 26 for connection with the final driveunit 22 of the vehicle is also provided. An output gear set 32 isdisposed between the output shaft 26 and the final drive unit 22. Aplanetary gear set 34 selectively couples the input shaft 24 and theoutput shaft 26.

The planetary gear set 34 includes a first sun gear 90 and a second sungear 92. The first sun gear 90 is connected to the input shaft 24between the first end 28 of the input shaft 24 and the second end 30 ofthe input shaft 24. The second sun gear 92 is connected to the inputshaft 24 between the first sun gear 90 and the second end 30 of theinput shaft 24. The planetary gear set 34 also includes at least a firstpinion gear 94 in meshing engagement with the first sun gear 90 and asecond pinion gear 96 in meshing engagement with the second sun gear 92.The first pinion gear 94 has a first outer diameter and the secondpinion gear 96 has a second outer diameter. The second outer diameter ofthe second pinion gear 96 is less than the first outer diameter of thefirst pinion gear 94. In other words, the second pinion gear 96 has asmaller circumference than the first pinion gear 94.

The planetary gear set 34 also includes a first ring gear 74 meshinglyengaged with the first pinion gear 94 and a second ring gear 76meshingly engaged with the second pinion gear 96. The first ring gear 74has a first inner diameter that circumscribes the first pinion gear 94and the first sun gear 90. Similarly, the second ring gear 76 has asecond inner diameter that circumscribes the second pinion gear 96 andthe second sun gear 92. Further, the first ring gear 74 and the secondring gear 76 are co-axially aligned and the second inner diameter of thesecond ring gear 76 is equal to the first inner diameter of the firstring gear 74.

The planetary gear set 34 includes a carrier 42 supporting at least thefirst pinion gear 94 and the second pinion gear 96. More specifically,the first pinion gear 94 and the second pinion gear 96 are radiallyoffset with respect to one another such that the smaller second piniongear 96 still meshes with the second ring gear 76. It should beappreciated that the second pinion gear 96 would not mesh with thesecond ring gear 76 if this offset were not provided given the co-axialalignment and symmetry of the inner diameters of the first ring gear 74and the second ring gear 76. It should also be appreciated that althoughthe first pinion gear 94 and the second pinion gear 96 are supported onthe carrier 42, they each may rotate with respect to the carrier 42 andindependently of one another.

A first mechanical diode 78 is connected to the first ring gear 74providing selective engagement of the first ring gear 74. A secondmechanical diode 80 is connected to the second ring gear 76 providingselective engagement of the second ring gear 76. The two-speedtransmission 20 further includes a multi-plate wet clutch assembly 50including a first brake 82 fixed to a ground 56 and a second brake 84also fixed to the ground 56. The first brake 82 includes a first brakefriction plate 86 connected to the first mechanical diode 78 and thesecond brake 84 includes a second brake friction plate 88 connected tothe second mechanical diode 80.

The multi-plate wet clutch assembly 50 provides a first gear ratio inresponse to the second brake 84 selectively engaging the second brakefriction plate 88 and the second mechanical diode 80 engaging the secondring gear 76. As such, in the first gear ratio, the multi-plate wetclutch assembly 50 resists rotation of the second ring gear 76 withrespect to the ground 56. The multi-plate wet clutch assembly 50provides a second gear ratio in response to the first brake 82selectively engaging the first brake friction plate 86 and the firstmechanical diode 78 engaging the first ring gear 74. As such, in thesecond gear ratio, the multi-plate wet clutch assembly 50 resistsrotation of the first ring gear 74 with respect to the ground 56.

The multi-plate wet clutch assembly 50 provides a neutral state inresponse to the first brake 82 permitting free rotation of the firstbrake friction plate 86 and the second brake 84 permitting free rotationof the second brake friction plate 88. In the neutral state, input shaft24, the first sun gear 90, and the second sun gear 92 rotate and driverotation of the first pinion gear 94 and the second pinion gear 96.Rotation of the first pinion gear 94 drives rotation of the first ringgear 74 and rotation of the second pinion gear 96 drives rotation of thesecond ring gear 76. The first ring gear 74 and the second ring gear 76rotate freely in the neutral state because the first and secondmechanical diodes 78, 80 and the first and second brakes 82, 84 are notengaged. Thus, all of the torque supplied to the input shaft 24 goes torotating the first and second ring gears 74, 76 so the carrier 42 is notrotationally driven. The carrier 42 is connected to the output shaft 26so the output shaft 26 is not rotationally driven in the neutral state.

The first gear ratio is provided in response to the first brake 82permitting free rotation of the first brake friction plate 86 when thefirst mechanical diode 78 is disengaged and the second brake 84selectively engaging the second brake friction plate 88 when the secondmechanical diode 80 is engaged. The second brake 84 and the secondmechanical diode 80 lock the second ring gear 76 in place so that thesecond ring gear 76 remains stationary with respect to the ground 56. Asthe input shaft 24 and the second sun gear 92 rotate and drive thesecond pinion gear 96, the second pinion gear 96 orbits within thesecond ring gear 76, traveling in a circular arc, as second pinion gear96 runs along the second ring gear 76. This orbital movement of thesecond pinion gear 96 with respect to the second ring gear 76 drivesrotation of the carrier 42 and thus the output shaft 26 at a rotationalspeed that may be different than a rotational speed of the input shaft24. At the same time, the first sun gear 90 rotates and drives the firstpinion gear 94, which in turn drives rotation of the first ring gear 74.The first ring gear 74 is allowed to freely rotate because the firstmechanical diode 78 and the first brake 82 are disengaged.

The second gear ratio is provided in response to the first brake 82selectively engaging the first brake friction plate 86 when the firstmechanical diode 78 is engaged and the second brake 84 permitting freerotation of the second brake friction plate 88 when the secondmechanical diode 80 is disengaged. The first brake 82 and the firstmechanical diode 78 lock the first ring gear 74 in place so that thefirst ring gear 74 remains stationary with respect to the ground 56. Asthe input shaft 24 and the first sun gear 90 rotate and drive the firstpinion gear 94, the first pinion gear 94 orbits within the first ringgear 74, traveling in a circular arc, as first pinion gear 94 runs alongthe first ring gear 74. This orbital movement of the first pinion gear94 with respect to the first ring gear 74 drives rotation of the carrier42 and thus the output shaft 26 at a rotational speed that may bedifferent than a rotational speed of the input shaft 24. At the sametime, the second sun gear 92 rotates and drives the second pinion gear96, which in turn drives rotation of the second ring gear 76. The secondring gear 76 is allowed to freely rotate because the second mechanicaldiode 80 and the second brake 84 are disengaged.

In another form of the configuration shown in FIG. 6, the two-speedtransmission 20 may also include one or more idler gears (not shown).For example, an idler gear may be disposed between the first pinion gear94 and the first sun gear 90. An idler gear may also be disposed betweenthe second pinion gear 96 and the second sun gear 92. Alternatively oradditionally, an idler gear may be disposed between the first piniongear 94 and the first ring gear 74. Similarly, an idler gear may bedisposed between the second pinion gear 96 and the second ring gear 76.It should be appreciated that one or none of the idler gears describedabove may be included in the two-speed transmission 20. It should alsobe appreciated that various combinations of the idler gears describedabove may be employed where all such combinations are considered to bewithin the scope of the subject disclosure.

Now referring to FIG. 7, another configuration of a two-speedtransmission 20 is illustrated. The two-speed transmission 20 includesan input shaft 24 and an output shaft 26. The input shaft 24 has a firstend 28 for connection with the electric motor and a second end 30opposite the first end 28. The output shaft 26 is provided forconnection with the final drive unit 22 of the vehicle. An output gearset 32 is disposed between the output shaft 26 and the final drive unit22. The two-speed transmission 20 also includes a planetary gear set 34selectively coupling the input shaft 24 and the output shaft 26. Theplanetary gear set 34 includes a sun gear 36, at least one double steppinion 38, a ring gear 40, and a carrier 42. The sun gear 36 isconnected to the input shaft 24 proximate to the second end 30 of theinput shaft 24. The at least one double step pinion 38 has a first gear44 and a second gear 46. The second gear 46 of the at least one doublestep pinion 38 is rotatably fixed with the first gear 44 of the at leastone double step pinion 38. The first gear 44 has a first outer diameterand the second gear 46 has a second outer diameter. The second outerdiameter of the second gear 46 is less than the first outer diameter ofthe first gear 44. The first gear 44 of the at least one double steppinion 38 is meshingly engaged with the sun gear 36 and is disposedradially outwardly of the sun gear 36.

The ring gear 40 is meshingly engaged with the second gear 46 of the atleast one double step pinion 38. Accordingly, the ring gear 40circumscribes the second gear 46 of the at least one double step pinion38. The carrier 42 supports the at least one double step pinion 38. Thecarrier 42 is connected to the output shaft 26 such that rotation of thecarrier 42 drives the output shaft 26. A dog clutch 48 is disposedadjacent the ring gear 40. The dog clutch 48 presents a plurality ofteeth providing selective interlocking engagement with the ring gear 40whether directly or through an intermediary component rotatably fixedwith the ring gear 40.

The two-speed transmission 20 also has a multi-plate wet clutch assembly50 including a brake 52 fixed to a ground 56 and a clutch 54 rotatablycoupled with the ring gear 40. The brake 52 includes a brake frictionplate 58 connected to the dog clutch 48. The brake 52 provides a firstgear ratio by selectively engaging the brake friction plate 58 to resistrotation of the ring gear 40 with respect to the ground 56 when the dogclutch 48 is engaged with the ring gear 40. The clutch 54 includes aclutch friction plate 62 connected to the input shaft 24 between thefirst end 28 of the input shaft 24 and the sun gear 36 of the planetarygear set 34. The clutch 54 provides a second gear ratio by selectivelyengaging the clutch friction plate 62 to rotatably couple the inputshaft 24 and the sun gear 36 with the ring gear 40. Accordingly, in thisconfiguration, the ring gear 40 is locked in rotation with the inputshaft 24 in response to the clutch 54 selectively engaging of the clutchfriction plate 62. This occurs because the clutch 54 is connected to thering gear 40. More particularly, the clutch 54 may include a clutchcaliper 64 that selectively engages the clutch friction plate 62. Thisclutch caliper 64 may be connected to the ring gear 40 to rotatablycouple the clutch 54 to the ring gear 40.

The multi-plate wet clutch assembly 50 of the two-speed transmission 20provides a neutral state in response to the brake 52 permitting freerotation of the brake friction plate 58 and the clutch 54 permittingfree rotation of the clutch friction plate 62. In the neutral state,input shaft 24 and the sun gear 36 rotate and drive rotation of thefirst gear 44 of the at least one double step pinion 38. Rotation of theat least one double step pinion 38 and thus the second gear 46 drivesrotation of the ring gear 40. The ring gear 40 rotates freely in theneutral state because the dog clutch 48 and the brake 52 are notengaged. Thus, all of the torque supplied to the input shaft 24 goes torotating the ring gear 40. The clutch 54 is disengaged so the carrier 42is not rotationally driven. The carrier 42 is connected to the outputshaft 26 so the output shaft 26 is not rotationally driven in theneutral state.

The first gear ratio is provided in response to the clutch 54 permittingfree rotation of the clutch friction plate 62 and the brake 52selectively engaging the brake friction plate 58 when the dog clutch 48is engaged. The brake 52 and the dog clutch 48 lock the ring gear 40 inplace so that the ring gear 40 remains stationary with respect to theground 56. As the input shaft 24 and the sun gear 36 rotate and drivethe first gear 44 of the at least one double step pinion 38, the atleast one double step pinion 38 orbits within the ring gear 40,traveling in a circular arc, as the second gear 46 of the at least onedouble step pinion 38 runs along the ring gear 40. This orbital movementof the at least one double step pinion 38 with respect to the ring gear40 drives rotation of the carrier 42 and thus the output shaft 26 at arotational speed that is different than a rotational speed of the inputshaft 24.

The second gear ratio is provided in response to the clutch 54selectively engaging the clutch friction plate 62 and the brake 52permitting free rotation of the brake friction plate 58 when the dogclutch 48 is not engaged. The clutch 54 locks rotation of the ring gear40 with the input shaft 24. Accordingly, the ring gear 40 rotates withthe sun gear 36. Rotation of the ring gear 40 drives rotation of thesecond gear 46 of the at least one double step pinion 38, which in turndrives rotation of the carrier 42 and thus the output shaft 26. In otherwords, the entire planetary gear set 34 rotates with the input shaft 24when the second gear ratio is selected.

In another configuration of the two-speed transmission 20 shown in FIG.7, one or more idler gears (not shown) may be employed. For example, anidler gear may be disposed between the first gear 44 of the at least onedouble step pinion 38 and the sun gear 36. Alternatively oradditionally, an idler gear may be disposed between the second gear 46of the at least one double step pinion 38 and the ring gear 40.

Now referring to FIG. 8, the two-speed transmission 20 of FIG. 7 may bemodified where the clutch friction plate 62 is connected to the carrier42 of the planetary gear set 34 instead of the input shaft 24. In thetwo-speed transmission 20 illustrated in FIG. 8, the multi-plate wetclutch assembly 50 includes the brake 52 fixed to the ground 56 and theclutch 54 rotatably coupled with the ring gear 40. The brake 52 of themulti-plate wet clutch assembly 50 provides a first gear ratio byselectively engaging the brake friction plate 58 to resist rotation ofthe ring gear 40 with respect to the ground 56 when the dog clutch 48 isengaged with the ring gear 40. The clutch friction plate 62 is connectedto the carrier 42 of the planetary gear set 34. The clutch 54 provides asecond gear ratio by selectively engaging the clutch friction plate 62to rotatably couple the carrier 42 and the ring gear 40. Because thecarrier 42 is also connected to the output shaft 26, selectiveengagement of the clutch friction plate 62 essentially locks the outputshaft 26 in rotation with the ring gear 40 such that the ring gear 40drives the output shaft 26.

The multi-plate wet clutch assembly 50 provides a neutral state inresponse to the brake 52 permitting free rotation of the brake frictionplate 58 and the clutch 54 permitting free rotation of the clutchfriction plate 62. In the neutral state, input shaft 24 and the sun gear36 rotate and drive rotation of the first gear 44 of the at least onedouble step pinion 38. Rotation of the at least one double step pinion38 and thus the second gear 46 drives rotation of the ring gear 40. Thering gear 40 rotates freely in the neutral state because the dog clutch48 and the brake 52 are not engaged. Thus, all of the torque supplied tothe input shaft 24 goes to rotating the ring gear 40. The clutch 54 isdisengaged so the carrier 42 is not rotationally driven. The carrier 42is connected to the output shaft 26 so the output shaft 26 is notrotationally driven in the neutral state.

The first gear ratio is provided in response to the clutch 54 permittingfree rotation of the clutch friction plate 62 and the brake 52selectively engaging the brake friction plate 58 when the dog clutch 48is engaged. The brake 52 and the dog clutch 48 lock the ring gear 40 inplace so that the ring gear 40 remains stationary with respect to theground 56. As the input shaft 24 and the sun gear 36 rotate and drivethe first gear 44 of the at least one double step pinion 38, the atleast one double step pinion 38 orbits within the ring gear 40,traveling in a circular arc, as the second gear 46 of the at least onedouble step pinion 38 runs along the ring gear 40. This orbital movementof the at least one double step pinion 38 with respect to the ring gear40 drives rotation of the carrier 42 and thus the output shaft 26 at arotational speed that is different than a rotational speed of the inputshaft 24.

The second gear ratio is provided in response to the clutch 54selectively engaging the clutch friction plate 62 and the brake 52permitting free rotation of the brake friction plate 58 when the dogclutch 48 is not engaged. The clutch 54 locks rotation of the ring gear40 with the carrier 42. Rotation of the at least one double step pinion38 drives rotation of the ring gear 40, which in turn drives rotation ofthe carrier 42 and thus the output shaft 26. In other words, the ringgear 40 and the carrier 42 rotate together when the second gear ratio isselected.

Now referring to FIG. 9, the two-speed transmission 20 of FIG. 1 may bemodified where the dog clutch 48 is connected to the brake 52. In thisconfiguration, the dog clutch 48 is arranged in selective engagementwith the ground 56 to selectively couple the brake 52 to the ground 56.The ground 56 may be for example a housing (not shown) of the two-speedtransmission 20. More specifically, the dog clutch 48 presents aplurality of teeth that may engage a component of the dog clutch 48 thatis fixed to the ground 56. When these teeth are interlockingly engaged,the dog clutch 48 is locked in place with respect to the ground 56.

The two-speed transmission 20 shown in FIG. 9 also includes amulti-plate wet clutch assembly 50 including a brake 52 and a clutch 54.The brake 52 includes a brake friction plate 58 connected to the ringgear 40. The brake 52 provides a first gear ratio of the two-speedtransmission 20 by selectively engaging the brake friction plate 58.When the brake 52 selectively engages the brake friction plate 58 andwhen the dog clutch 48 selectively engages the ground 56, the brake 52resists rotation of the brake friction plate 58 with respect to theground 56. This correspondingly restricts rotation of the ring gear 40with respect to the ground 56 when the dog clutch 48 is engaged with theground 56. More particularly, the brake 52 may include a brake caliper60 that selectively engages the brake friction plate 58.

In FIG. 9, the multi-plate wet clutch assembly 50 of the two-speedtransmission 20 provides a neutral state in response to the clutch 54permitting free rotation of the clutch friction plate 62 and the brake52 permitting free rotation of the brake friction plate 58. In theneutral state, input shaft 24 and the sun gear 36 rotate and driverotation of the first gear 44 of the at least one double step pinion 38.Rotation of the at least one double step pinion 38 and thus the secondgear 46 drives rotation of the ring gear 40. The ring gear 40 rotatesfreely in the neutral state because the dog clutch 48 and the brake 52are not engaged. Thus, all of the torque supplied to the input shaft 24goes to rotating the ring gear 40 so the carrier 42 is not rotationallydriven. The carrier 42 is connected to the output shaft 26 so the outputshaft 26 is not rotationally driven in the neutral state.

The first gear ratio is provided in response to the clutch 54 permittingfree rotation of the clutch friction plate 62 and the brake 52selectively engaging the brake friction plate 58 when the dog clutch 48is engaged. The brake 52 and the dog clutch 48 lock the ring gear 40 inplace so that the ring gear 40 remains stationary with respect to theground 56. As the input shaft 24 and the sun gear 36 rotate and drivethe first gear 44 of the at least one double step pinion 38, the atleast one double step pinion 38 orbits within the ring gear 40,traveling in a circular arc, as the second gear 46 of the at least onedouble step pinion 38 runs along the ring gear 40. This orbital movementof the at least one double step pinion 38 with respect to the ring gear40 drives rotation of the carrier 42 and thus the output shaft 26 at arotational speed that is different than a rotational speed of the inputshaft 24.

The second gear ratio is provided in response to the clutch 54selectively engaging the clutch friction plate 62 and the brake 52permitting free rotation of the brake friction plate 58. The clutch 54locks rotation of the carrier 42 with the input shaft 24. Therefore, thecarrier 42 and thus the output shaft 26 rotate at the same rotationalspeed as the input shaft 24. Accordingly, the second gear ratio may be a1:1 ratio.

The foregoing description of the embodiments has been provided for thepurposes of illustration and description. It is not intended to beexhaustive or limiting. Obviously, many modifications and variations ofthe present disclosure are possible in light of the above teachings andmay be practiced otherwise than as specifically described while withinthe scope of the appended claims.

What is claimed is:
 1. A two-speed transmission that transfers torquefrom a motor to a final drive unit, comprising: an input shaft having afirst end that connects with the motor and a second end opposite saidfirst end; an output shaft that connects with the final drive unit; aplanetary gear set selectively coupling said input shaft and said outputshaft; said planetary gear set including a sun gear connected to saidinput shaft; said planetary gear set including at least one pinionhaving a first gear and a second gear rotatably fixed with said firstgear; said first gear having a first diameter and said second gearhaving a second diameter that is different than said first diameter;said first gear of said at least one pinion being meshingly engaged withsaid sun gear and disposed radially outwardly of said sun gear; saidplanetary gear set including a ring gear meshingly engaged with saidsecond gear of said at least one pinion and circumscribing said secondgear of said at least one pinion; said planetary gear set including acarrier connected to said output shaft and supporting said at least onepinion; a brake fixed to a ground; and a dog clutch selectively couplingsaid ring gear and said brake, said brake providing a first gear ratioby resisting rotation of said ring gear with respect to said ground whensaid brake and said dog clutch are engaged.
 2. The two-speedtransmission of claim 1 further comprising: a friction clutch connectedto said carrier and said input shaft, said friction clutch providing asecond gear ratio by rotatably coupling said input shaft and saidcarrier when said friction clutch is engaged.
 3. The two-speedtransmission of claim 2 wherein said brake and said dog clutch provideneutral by permitting free rotation of said ring gear while saidfriction clutch permits free rotation of said input shaft.
 4. Thetwo-speed transmission of claim 2 wherein said friction clutch includesa clutch friction plate connected to said input shaft between said firstend of said input shaft and said sun gear of said planetary gear set anda clutch caliper connected to said carrier, where said friction clutchselectively engages said clutch friction plate to rotatably couple saidinput shaft and said carrier when said second gear ratio is selected. 5.The two-speed transmission of claim 1 further comprising: a frictionclutch connected to said ring gear and said input shaft, said frictionclutch providing a second gear ratio by rotatably coupling said inputshaft and said ring gear when said friction clutch is engaged.
 6. Thetwo-speed transmission of claim 5 wherein said brake and said dog clutchprovide neutral by permitting free rotation of said ring gear while saidfriction clutch permits free rotation of said input shaft.
 7. Thetwo-speed transmission of claim 5 wherein said friction clutch includesa clutch friction plate connected to said input shaft between said firstend of said input shaft and said sun gear of said planetary gear set anda clutch caliper connected to said ring gear, where said friction clutchselectively engages said clutch friction plate to rotatably couple saidinput shaft and said ring gear when said second gear ratio is selected.8. The two-speed transmission of claim 1 further comprising: a frictionclutch connected to said carrier and said ring gear, said frictionclutch providing a second gear ratio by rotatably coupling said ringgear and said carrier when said friction clutch is engaged.
 9. Thetwo-speed transmission of claim 8 wherein said brake and said dog clutchprovide neutral by permitting free rotation of said ring gear while saidfriction clutch permits free rotation of said carrier.
 10. The two-speedtransmission of claim 8 wherein said friction clutch includes a clutchfriction plate connected to said carrier of said planetary gear set anda clutch caliper connected to said ring gear, where said friction clutchselectively engages said clutch friction plate to rotatably couple saidring gear and said carrier when said second gear ratio is selected. 11.The two-speed transmission of claim 1 wherein said brake includes abrake friction plate connected to said dog clutch, where said dog clutchselectively engages said ring gear and said brake selectively engagessaid brake friction plate to resist rotation of said ring gear withrespect to said ground when said first gear ratio is selected.
 12. Thetwo-speed transmission of claim 1 wherein said dog clutch includes aplurality of teeth that interlockingly engage said ring gear when saiddog clutch is actuated to couple said ring gear and said brake.
 13. Thetwo-speed transmission of claim 1 wherein said dog clutch includes aplurality of teeth that interlockingly engage a component of said dogclutch that is fixed to said ground when said dog clutch is actuated tocouple said ground and said brake.
 14. The two-speed transmission ofclaim 1 wherein said brake is part of a multi-plate clutch assembly. 15.The two-speed transmission of claim 1 wherein said brake is part of awet clutch assembly.